1. Field of the Invention
The present invention relates to An OTDR light reflection structure of optical sub-assembly for transceivers of PON system.
2. Description of the Related Art
Following the rapid growth of global Internet, the traditional networks have become unable to satisfy the demands for high-speed information transmission application caused by communication revolution. The matured photonic technologies and diversified products have duly provided a solution to the requirement for mass bandwidths of the global Internet, high-quality and multimedia networks and various data communications. Accordingly, various optical communication network frameworks have been successively developed, such as passive optical network (PON) system. The PON system must employ an optical time domain reflectometer (OTDR) for measuring quality of the optical fiber and detecting failures.
In general, the PON system can be a 1-to-8, 1-to-16 or 1-to-32 multi-optical fiber framework. The OTDR can monitor and detect failures within a few kilometers. However, the OTDR cannot find out which optical fiber is with the problem. In maintenance, it is inevitable to exactly find the failure and effectively remove the failure.
Currently, the optical sub-assembly for transceivers, such as bi-direction optical sub-assembly (BOSA) and tri-direction optical sub-assembly (TRI-DI OSA), installed at a subscriber terminal is not provided with any device or function for reflecting back the light emitted from the OTDR. After leaving the optical fiber, the light will scatter and cannot be reflected and focused back to the optical fiber. As shown in FIG. 1, in order to for the subscriber terminal to transmit a feedback signal to the OTDR 12 for the OTDR 12 to accurately judge the condition of the optical cable of the network, an OTDR light reflection device 11 is installed outside the BOSA or TRI-DI OSA 10 to reflect the signal back to the OTDR 12. However, the OTDR light reflection device 11 is an external added device. For a multi-optical fiber PON system, it is necessary to install several OTDR light reflection devices 11. The OTDR light reflection device 11 is quite expensive so that the solution will result in considerable increase of cost.